update music library

I have some new music to add to my ipod. I also have some music on it that I no longer want. I was thinking, remove all audio files from library onto my external hard drive in a new folder. Then add in all the new music I want on my ipod. Finally I would then upload all the wanted audio back to iTunes then update my ipod.

Thing is I'm not sure if it is as simple or easy as that sounds. Not a computer or iTunes whizz but I'm not too bad with them either. Anyone have detailed instructions on how to do what I want to do?

Thanks.